1. Field of the Invention
The present invention relates to a target device for an X-ray examination installation, and in particular to a target device which permits loading of an X-ray film cassette in the device from either the left or the right side.
1. Description of the Prior Art
Conventional targets for X-ray examination installations generally exhibit a luminescent screen aligned with the radiation cone, which is usually a component of an X-ray image intensifier. Such conventional devices also include a radiation-protected ready position for an X-ray film cassette which, as viewed by a person standing in front of the device, is generally situated at the right of the device next to the luminescent screen. As needed, such as when a finding to be documented is observed during radioscopy, the X-ray film cassette can be introduced into the radiation cone by operating a control button which causes the cassette to be moved from the ready position to an exposure position within the radiation cone, situated directly in front of the luminescent screen in the direction of radiation propogation. For this purpose, the X-ray film cassette is generally clamped in a cassette carriage which is motor driven from the ready position into a variety of exposure positions, and subsequently returned to the ready position.
After the film in the X-ray film cassette is exposed, the cassette carriage together with the X-ray film cassette is transported back to the ready position. The target device housing is generally open in a direction toward the attendant or operator in the area of the ready position. The X-ray film cassette in the ready position can therefore generally be obliquely placed from the top onto the lower horizontal clamping jaw and, by the application of downward pressure, is inserted below the upper clamping jaw, which is generally parallel to the aforementioned horizontal clamping jaw. If a physician is operating the machine, the physician is normally situated to the left of the exposure position in order to obtain better accessibility to the patient as well as to be in a convenient position for operating the X-ray installation controls. In conventional devices when the X-ray film cassette disposed in the cassette carriage must be replaced with another cassette with an unexposed sheet of film, the physician (if no assistant is available) must move around the bulky X-ray image intensifier disposed in front of the exposure position in order to change the X-ray film cassette in the ready position. Such movement is inconvenient and time consuming.
One attempted solution to the above-described problem is an X-ray examination unit wherein the target device has a cassette insertion slot located at its front edge at the left side next to the exposure position, by means of which changing of the X-ray film cassette can be achieved. For this purpose, the cassette carriage employed for transporting the X-ray film cassette from the ready position to the various exposure positions is able to be further transported from the ready position beyond the exposure position to a left side loading position. A disadvantage of such installations, however, is that the front side of the new X-ray film cassette cannot be inserted without difficulty from the left through the cassette insertion slot between the clamping jaws of the cassette carriage. This is because the jaws are necessarily urged together such that a small spacing remains between the jaws by means of a tension spring. This requires the physician to pull the lower clamping jaw with one hand and to insert the X-ray film cassette into the slot between the two clamping jaws up to the detent with his or her other hand. Only then can the lower clamping jaw be released. This maneuver requires the physician to release the command arm and other controls for the X-ray installation and to direct his or her attention entirely to the removal of the old cassette and insertion of the new X-ray cassette.
Another X-ray examination installation is described in German AS 2 333157 wherein interchanging the X-ray film in the ready position, for example by right side loading, is entirely eliminated and the cassette can only be loaded from the left side. For this purpose the clamping jaws are urged apart by means of a spring. A further tension spring is secured to the clamping jaws and forces the jaws against the newly-inserted X-ray film cassette as soon as the tension spring is tensed upon insertion of the X-ray film cassette into the cassette carriage. Although left side loading is facilitated in this X-ray examination means, right side loading is omitted altogether.